CaltechAUTHORS
Published November 24, 2022 | Version public
Journal Article Metadata-only

Polarized blazar X-rays imply particle acceleration in shocks

Creators

  • 1. ROR icon University of Turku
  • 2. ROR icon Boston University
  • 3. ROR icon Instituto de Astrofísica de Andalucía
  • 4. ROR icon Brera Astronomical Observatory
  • 5. ROR icon FORTH Institute of Astrophysics
  • 6. ROR icon University of Crete
  • 7. ROR icon Agenzia Spaziale Italiana
  • 8. ROR icon Washington University in St. Louis
  • 9. ROR icon Stanford University
  • 10. ROR icon Marshall Space Flight Center
  • 11. ROR icon St Petersburg University
  • 12. ROR icon Tohoku University
  • 13. ROR icon Kavli Institute for Particle Astrophysics and Cosmology
  • 14. ROR icon Observatory of Strasbourg
  • 15. ROR icon University of Siena
  • 16. ROR icon Massachusetts Institute of Technology
  • 17. ROR icon INFN Sezione di Torino
  • 18. ROR icon University of Turin
  • 19. ROR icon Infrared Processing and Analysis Center
  • 20. ROR icon California Institute of Technology
  • 21. ROR icon Astronomical Observatory of Rome
  • 22. ROR icon University of California, Santa Barbara
  • 23. ROR icon University of Maryland, Baltimore County
  • 24. ROR icon Institute for Space Astrophysics and Planetology
  • 25. ROR icon Osservatorio Astrofisico di Torino
  • 26. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 27. ROR icon Space Research Institute
  • 28. ROR icon Special Astrophysical Observatory
  • 29. ROR icon Pulkovo Observatory
  • 30. ROR icon University of California, Santa Cruz
  • 31. ROR icon INFN Sezione di Pisa
  • 32. ROR icon University of Pisa
  • 33. ROR icon Roma Tre University
  • 34. ROR icon Arcetri Astrophysical Observatory
  • 35. ROR icon University of Florence
  • 36. ROR icon National Institute for Nuclear Physics
  • 37. ROR icon INFN Sezione di Roma II
  • 38. ROR icon University of Tübingen
  • 39. ROR icon Astronomical Institute
  • 40. ROR icon RIKEN
  • 41. ROR icon Yamagata University
  • 42. ROR icon Osaka University
  • 43. ROR icon University of British Columbia
  • 44. ROR icon Chuo University
  • 45. ROR icon Nagoya University
  • 46. ROR icon Hiroshima University
  • 47. ROR icon University of Hong Kong
  • 48. ROR icon Pennsylvania State University
  • 49. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 50. ROR icon University of Padua
  • 51. ROR icon University of Rome Tor Vergata
  • 52. ROR icon University College London
  • 53. ROR icon University of Amsterdam
  • 54. ROR icon Guangxi University

Abstract

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization—the only range available until now—probe extended regions of the jet containing particles that left the acceleration site days to years earlier, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree ΠX of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock.

Additional Information

I.L. thanks the Kavli Institute for the Physics and Mathematics of the Universe for their hospitality while this paper was written. We thank A. Veledina for discussions that helped improve this work. I.L. was supported by the JSPS postdoctoral short-term fellowship programme. The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). Data from the Steward Observatory spectropolarimetric monitoring project were used. This programme is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G and NNX15AU81G. This research has made use of data from the RoboPol programme, a collaboration between Caltech, the University of Crete, the Institute of Astrophysics-Foundation for Research and Technology (IA-FORTH), the Inter-University Centre for Astronomy and Astrophysics (IUCAA), the Max Planck Institute for Radioastronomy (MPIfR) and the Nicolaus Copernicus University, which was conducted at Skinakas Observatory in Crete, Greece. The Instituto Astrofísica Andalucía (IAA)-Consejo Superior de Investigaciones Científicas (CSIC) co-authors acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion (MCINN) through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia-CSIC (SEV-2017-0709). Acquisition and reduction of the POLAMI and Monitoring AGN with Polarimetry at the Calar Alto Telescopes (MAPCAT) data were supported in part by Ministerio de Ciencia e Innovación (MICINN) through grants AYA2016-80889-P and PID2019-107847RB-C44. The POLAMI observations were carried out at the IRAM 30 m Telescope. IRAM is supported by the National Institute of Sciences of the Universe (INSU)/Scientific Research National Center (CNRS) (France), Max-Planck-Gesellschaft (MPG) (Germany) and Instituto Geográfico Nacional (IGN) (Spain). The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917 and NASA Swift Guest Investigator grant 80NSSC22K0537. This study uses observations conducted with the 1.8 m Perkins Telescope Observatory in Arizona (USA), which is owned and operated by Boston University. Based on observations obtained at the Hale Telescope, Palomar Observatory as part of a continuing collaboration between the California Institute of Technology, NASA/Jet Propulsion Laboratory (JPL), Yale University and the National Astronomical Observatories of China. This research made use of Photutils, an Astropy package for detection and photometry of astronomical sources60. G.V.P. acknowledges support by NASA through the NASA Hubble Fellowship grant no. HST-HF2-51444.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained (in part) with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and the Nordic Optical Telescope. V.K. thanks the Vilho, Yrjö and Kalle Väisälä Foundation. J.J. was supported by Academy of Finland project 320085. E.L. was supported by Academy of Finland projects 317636 and 320045. Part of the French contribution was supported by the CNRS and the French spatial agency (CNES). Based on observations collected at the Observatorio de Sierra Nevada, owned and operated by the Instituto de Astrofisica de Andalucia (IAA-CSIC). Based on observations collected at the Centro Astronomico Hispano-Aleman (CAHA), proposal 22A-2.2-015, operated jointly by Junta de Andalucia and Consejo Superior de Investigaciones Cientificas (IAA-CSIC). Open access funding provided by University of Turku (UTU) including Turku University Central Hospital.

Additional details

Identifiers

PMCID
PMC9684068
Eprint ID
118318
Resolver ID
CaltechAUTHORS:20221212-796684400.32

Funding

Japan Society for the Promotion of Science (JSPS)
NASA
NNM15AA18C
Agenzia Spaziale Italiana (ASI)
ASI-OHBI-2017-12-I.0
Agenzia Spaziale Italiana (ASI)
ASI-INAF-2017-12-H0
Agenzia Spaziale Italiana (ASI)
ASI-INFN-2017.13-H0
Agenzia Spaziale Italiana (ASI)
ASI-INAF-2022-14-HH.0
Agenzia Spaziale Italiana (ASI)
ASI-INFN 2021-43-HH.0
Istituto Nazionale di Astrofisica (INAF)
Istituto Nazionale di Fisica Nucleare (INFN)
NASA
NNX08AW56G
NASA
NNX09AU10G
NASA
NNX12AO93G
NASA
NNX15AU81G
Severo Ochoa
SEV-2017-0709
Ministerio de Economía y Competitividad (MINECO)
AYA2016-80889-P
Ministerio de Ciencia e Innovación (MICINN)
PID2019-107847RB-C44
Centre National de la Recherche Scientifique (CNRS)
Max-Planck-Gesellschaft (MPG)
Instituto Geográfico Nacional (IGN)
NSF
AST-2108622
NASA
80NSSC21K1917
NASA
80NSSC22K0537
NASA/JPL/Caltech
NASA Hubble Fellowship
HST-HF2-51444.001-A
NASA
NAS5-26555
Vilho Foundation
Yrjö Foundation
Kalle Väisälä Foundation
Academy of Finland
320085
Academy of Finland
317636
Academy of Finland
320045
Centre National d'Études Spatiales (CNES)
University of Turku
Turku University Central Hospital

Dates

Created
2023-01-13
Created from EPrint's datestamp field
Updated
2023-03-16
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Astronomy Department, Infrared Processing and Analysis Center (IPAC), Space Radiation Laboratory